Method for producing a substrate arrangement

ABSTRACT

The invention relates to a method for producing a substrate arrangement with the process steps:  
     preparation of a substrate and bringing connecting surfaces of the substrate into contact with inner contacts of a wiring layer,  
     application of contact material to outer contacts of the wiring layer defining an outer connecting surface arrangement to form base contact bumps ( 31 ) and  
     application of joining material to the base contact bumps to form contact bump tops joined to the base contact bumps, wherein the joining material is applied as joining material moldings ( 35 ) and the contact bump tops are formed by at least partial melting of the joining material moldings by the action of laser energy.

[0001] The present invention relates to a method for producing asubstrate arrangement with the process steps:

[0002] preparation of a substrate and bringing connecting surfaces ofthe substrate into contact with inner contacts of a wiring layer,

[0003] application of contact material to outer contacts of the wiringlayer defining an outer connecting surface arrangement to form basecontact bumps and

[0004] application of joining material to the base contact bumps to formcontact bump tops joined to the base contact bumps.

[0005] Methods of the preceding type are used to produce substratearrangements, for example, chip arrangements with a chip or a chipmodule as the substrate. Such chip arrangements are frequently alsotermed so-called “chip size packages”. These chip arrangements firstlymake it possible to redistribute the peripherally arranged connectingsurfaces of a chip for a subsequent contacting with further componentsor substrates. Secondly, such chip arrangements should ensure aconnection contact with high mechanical reliability because of itsincreased mechanical stability compared with the chip. Provided for thispurpose are raised contact bumps each having a base contact bumpconstructed in column form and a contact bump top arranged thereon. As aresult of the raised formation of the contact bumps, the stressesappearing in the contact region between a chip arrangement and asubstrate in contact with it as a result of the different coefficientsof thermal expansion of the chip and the substrate should be reduced asfar as possible.

[0006] A method of the type specified initially is known from DE 197 54372 A1 wherein the raised contact bumps are formed by first producingthe base contact bumps on the outer contacts of the wiring layer in areflow method, then embedding the base contact bumps in a matrixmaterial applied to the wiring layer and hardening the matrix material.Matrix material is then removed from the surface to expose or produce anarrangement of contact surfaces of the base contact bumps flush in thematrix material. Finally contact bump tops are formed by applyingjoining material to the plane contact surfaces of the base contact bumpsand then melting the joining material in the reflow method.

[0007] In the method known from DE 197 54 372 A1 it is thus necessary toremove material from the surface between the formation of the basecontact bumps and the formation of the contact bump tops on the basecontact bumps in order to form the contact surfaces on the base contactbumps. In addition, regardless of the type of subsequent contacting ofthe chip arrangement with a substrate, because the contact bump tops areformed using the reflow method, it is necessary to prepare a supportmatrix which mechanically supports the base contact bumps to stabilizetheir shape by means of the hardened matrix material.

[0008] The object of the present invention is to propose a method forproducing a substrate arrangement of the type specified initially whichallows simplified production of the substrate arrangement.

[0009] This object is achieved using a method having the features ofclaim 1.

[0010] In the method according to the invention the joining material isapplied as joining material moldings and the contact bump tops areformed by at least partial melting of the joining material moldings byapplication of laser energy.

[0011] Compared with the known method, the method according to theinvention thus has the advantage that as a result of the melting of thejoining material moldings using laser energy, locally delimited, exactlydefinable thermal energy can be produced in the joining materialmoldings so that the melting of the joining material moldings to formthe contact bump tops does not necessarily involve any melting of thebase contact bumps. Thus, a support matrix to ensure that the basecontact bumps retain their shape during the formation of the contactbump tops can be dispensed with. Consequently, there is no need for anyremoval of material to form contact surfaces between the base contactbumps and the contact bump tops.

[0012] In the event that contact between the chip arrangement producedaccording to the invention and a substrate should be made in a reflowmethod, according to one variant of the method it is possible to applymatrix material to receive the base contact bumps in an embeddingfashion following the formation of the base contact bumps and precedingthe formation of the contact bump tops.

[0013] If the matrix material has flux properties, i.e., for example, isconstructed as a polymer flux material, the base contact bumps can becovered by the matrix material and before application of the joiningmaterial moldings to the base contact bumps or during the formation ofthe contact bump tops, the matrix material can be activated in thecontact region on the base contact bumps by exposure to laser energy. Inthis connection, it is found to be especially advantageous if the matrixmaterial in the contact regions and the joining material moldings aremore or less simultaneously exposed to produce the structural joinbetween the contact bump tops and the base contact bumps.

[0014] Following the formation of the contact bump tops, it is alsopossible to apply a matrix material to receive the base contact bumpsand the contact bump tops in an embedding fashion in order to keep theassociated reduction in the height of the contact bump structure assmall as possible during the subsequent contacting of the chiparrangement with a substrate in the reflow method.

[0015] If following the formation of the base contact bumps andpreceding the formation of the contact bump tops, a matrix material toreceive the base contact bumps in an embedding fashion is applied suchthat the base contact bumps are covered by the matrix material, it isfound to be advantageous to ablate the matrix material arranged in acontact region on the base contact bumps by exposing it to laser energybefore applying the joining material moldings to the base contact bumps.Even if the material matrix comprises a hardened artificial resinstructure, it is thus possible to dispense with the removal of materialfrom a large area, unlike the method known from DE 197 54 372 A1, andablate the matrix material merely in the actual contact regions. In thiscase, it is possible to use exactly the same laser device as is used forthe subsequent melting of the joining material moldings to form thecontact bump tops.

[0016] Especially if the matrix material has flux properties, anyremoval of the matrix material covering the base contact bumps can bedispensed with and rather, by applying the joining material moldings tothe base contact bumps, the matrix material can be displaced in thecontact regions on the base contact bumps. If necessary, thisdisplacement can be preceded by liquefaction of the matrix material inthe contact regions on the base contact bumps.

[0017] It can also be advantageous if the joining material moldings areapplied to the base contact bumps covered by the matrix material, thematrix material is locally liquefied in the region of the base contactbumps by laser action and on application of the joining materialmoldings to the base contact bumps, the matrix material is displaced incontact regions with the joining material moldings.

[0018] If the matrix material is transferred to the solid state afterdisplacement of the matrix material in contact regions with the joiningmaterial moldings, it is possible to merely selectively harden thematrix material and remove excess, still liquid, matrix material, by aflushing process for example.

[0019] Especially if the matrix material is polymer-based, for example,as polymer flux, the matrix material can be transferred to the solidstate by polymerization.

[0020] Polymerization can be achieved, for example, by local action oflaser energy on the matrix material in the peripheral region of thecontact bump tops.

[0021] Especially in this connection, it is found to be particularlyadvantageous if a material provided with additives to reduce oxides atleast on its surface is used as matrix material.

[0022] Preferred variants of the method for producing a chip arrangementare described in detail in the following with reference to the drawingswherein:

[0023]FIG. 1 shows the application of solder material moldings to formbase contact bumps on connecting surfaces of a wiring layer arranged ona chip;

[0024]FIG. 2 shows the base contact bumps formed on the connectingsurfaces;

[0025]FIG. 3 shows the base contact bumps embedded in a matrix materialon the wiring layer;

[0026]FIG. 4 shows the base contact bumps embedded in matrix materialand exposed from matrix material in a contact region;

[0027]FIG. 5 shows the application of joining material moldings to thecontact region of the base contact bumps;

[0028]FIG. 6 shows the base contact bumps provided with contact bumptops;

[0029]FIG. 7 shows the application of joining material moldings toexposed base contact bumps;

[0030]FIG. 8 shows the base contact bumps provided with contact bumptops;

[0031]FIG. 9 shows the application of joining material moldings to basecontact bumps covered by matrix material;

[0032]FIG. 10 shows the application of joining material moldings to basecontact bumps covered by a matrix material film;

[0033]FIG. 11 shows the contacting of base contact bumps by joiningmaterial moldings to form contact bump tops with simultaneousliquefaction of the matrix material in the contact region;

[0034]FIG. 12 shows the base contact bumps provided with contact bumptops.

[0035]FIG. 1 shows a semiconductor substrate constructed as a chip 20provided with chip connecting surfaces 22 on a contact surface 21. Thechip connecting surfaces 22 are contacted by inner contacts 23 of awiring layer 24 which are connected to outer contacts 27 via aconducting path structure 26 of the wiring layer 24. The outer contacts27 have a distribution in an outer contact surface 28 of the wiringlayer 24 which differs from the inner contacts 23 or the chip connectingsurfaces 22.

[0036]FIG. 1 shows how, starting from the chip 20 in contact with thewiring layer 24, joining material moldings 29 constructed as sphericalin the present case, are applied by means of a template 25 in anarrangement corresponding to the arrangement of the outer contacts 27 ofthe wiring layer 24.

[0037] The joining material moldings 29 are then exposed to laser energy30 using a laser device, not shown in detail here, in order to melt thejoining material moldings 29 formed of solder material, for example, towet the outer contacts 27 of the wiring layer 24 and form base contactbumps 31 as shown in FIG. 2.

[0038] Following the formation of the base contact bumps 31, as shown inFIG. 3, a matrix material 32 in liquid form is applied to the wiringlayer 24 to embed the base contact bumps 31 with a covering cladding. Asshown further in FIG. 3, after hardening the matrix material 32 formedof an artificial resin base, for example, to form a support matrix 33stabilizing the external shape of the base contact bumps 31, the matrixmaterial 32 is exposed to laser energy 30 in the contact regions 34 onthe base contact bumps 31 to ablate the matrix material 32 in thecontact regions 34, as shown in FIG. 4.

[0039] After the contact regions 34 on the base contact bumps 31 havebeen exposed, joining material moldings 35 are applied to the basecontact bumps 31 in the contact regions 34, as shown in FIG. 5. Byanalogy with the application of the joining material moldings 29 to theouter contacts 27 of the wiring layer 24, a defined arrangement of thejoining material moldings 35 on the base contact bumps 31 is achieved bymeans of a template 25. As then shown in FIG. 5, the joining materialmoldings 35 applied to the base contact bumps 31 are then exposed tolaser energy 30 in order to melt the joining material moldings 35 andwet the base contact bumps 31 in the contact regions 34 to form contactbump tops 37 on the base contact bumps 31 as shown in FIG. 6 so that anoverall chip arrangement 38 is formed, comprising the chip 20 and thewiring layer 24 with raised contact bumps 39. In this case, it is foundto be advantageous if the joining material to form the base contactbumps 31 has a higher melting point than the joining material formingthe contact bump tops 37.

[0040] For example, possible joining materials for the joining materialmoldings 29, 35 may be conventional solder material, metal, especiallyhigher-melting metal with a solder material coating or a polymermaterial with a solder material coating.

[0041] As shown in FIG. 6 by a contact substrate 40 shown as a dashedline, following the completion of the chip arrangement 38, the contactbumps 39 can be brought in contact with the connecting surfaces 41 ofthe contact substrate 40. This contacting can be accomplished by wettingthe at least partly melted contact bumps 39 in a conventional fashionusing the reflow method. Especially in the case of a transparent contactsubstrate 40, it is also possible to achieve partial melting of thecontact bumps 39 which can be metered exactly in a contact region 42with the connecting surfaces 41 by rearward exposure of the connectingsurfaces 41 of the contact substrate 40 to laser energy 30, as indicatedin FIG. 6.

[0042]FIG. 7 shows a variant of the method wherein the application of asupport matrix 33 to the wiring layer 24 is dispensed with and startingfrom the state of the method shown in FIG. 2, characterized by theexposed arrangement of the base contact bumps 31 on the outer contacts25 of the wiring layer 24, the joining material moldings 35 are appliedto the base contact bumps 31 by means of the template 25.

[0043] Following the application of the joining material moldings 35 tothe base contact bumps 31, the joining material moldings 35 are exposedto laser energy 30 to melt the joining material moldings 35 with wettingof the base contact bumps 31 and forming of contact bump tops 37 asshown in FIG. 8.

[0044] As also shown in FIG. 8, a chip arrangement 43 as shown in FIG.8, which has no support matrix 33 unlike the chip arrangement 38 shownin FIG. 6, is subsequently brought in contact with a contact substrate40 such that connecting surfaces 41 of the contact substrate 40 arerearwardly exposed to laser energy 30 through the transparent contactsubstrate 40 in order to merely locally melt the contact bump tops 37 inthe immediate contact region 42 with the connecting surfaces 41 andproduce contacting wetting of the contact bump tops 37 on the connectingsurfaces 41 in the contact region 42.

[0045] Another variant of the method is shown in FIGS. 9, 10, 11 and 12wherein the joining material moldings 35 are applied starting from thestate of the process shown in FIG. 3 wherein the base contact bumps 31formed on the connecting surfaces 27 of the wiring layer 24 are coveredwith matrix material 32. Starting from the base contact bumps 31 thuscompletely embedded in the support matrix 33 as shown in FIG. 9, thejoining material moldings 35 are applied to a matrix surface 44 abovecontact regions of the base contact bumps 31. This is thenadvantageously followed by application of pressure to the joiningmaterial moldings 35 generated by an optical fiber 45 preceded by, or atthe same time as, exposure of the matrix surface 44 to laser energy 30in the contact region 46 of the joining material moldings 35 with thematrix material 32 to liquefy the matrix material 32. Alternatively oradditionally, laser energy can be applied through the optical fiber 45.

[0046] Instead of the large volume of matrix material 32 comparedrelative to the height of the base contact bumps 31 as in FIG. 9, it isalso possible to make the volume of the matrix material 32 such thatonly the upper sides of the base contact bumps 31 are wetted as shown inFIG. 10.

[0047] As shown in FIG. 11, as a result of the application of pressureto the joining material moldings 35 by means of the optical fibers 45,matrix material 32 liquefied in the contact region 46 is displaced toproduce a body contact between the joining material moldings 35 and thebase contact bumps 31. If the matrix material 32 has flux properties,laser energy 30 can be applied to the joining material moldings 35through the optical fibers 45 to melt the joining material moldings 35with wetting of the base contact bumps 31 and forming of contact bumptops 37 as shown in FIG. 12.

1. A method for producing a substrate arrangement (38, 43) with theprocess steps: preparation of a substrate (20) and bringing connectingsurfaces (22) of the substrate into contact with inner contacts (23) ofa wiring layer (24), application of contact material (29) to outercontacts (27) of the wiring layer (24) defining an outer connectingsurface arrangement to form base contact bumps (31) and application ofjoining material to the base contact bumps to form contact bump tops(37) joined to the base contact bumps, characterized in that the joiningmaterial is applied as joining material moldings (35) and the contactbump tops (37) are formed by at least partial melting of the joiningmaterial moldings by application of laser energy (30).
 2. The methodaccording to claim 1, characterized in that following the formation ofthe base contact bumps (31) and preceding the formation of the contactbump tops (37), a matrix material (32) receiving the base contact bumps(31) in an embedding fashion is applied.
 3. The method according toclaim 2, characterized in that the base contact bumps (31) are coveredby the matrix material (32) and before the joining material moldings(35) are applied to the base contact bumps (31) or during the formationof the contact bump tops (37), the matrix material (32) arranged in acontact region with the joining material moldings (35) is exposed tolaser energy (30).
 4. The method according to claim 1, characterized inthat following the formation of the contact bump tops (37) a matrixmaterial (32) receiving the base contact bumps (31) and the contact bumptops (37) in an embedding fashion is applied.
 5. The method according toclaim 2, characterized in that the base contact bumps (31) are coveredby the matrix material (32) and before the joining material moldings(35) are applied to the base contact bumps (31), the matrix material(32) arranged in a contact region (34) on the base contact bumps (31) isablated by exposure to laser energy (30).
 6. The method according toclaim 2, characterized in that the base contact bumps (3 1) are coveredby the matrix material (32) and during application of the joiningmaterial moldings (35) to the base contact bumps (31), the matrixmaterial (32) is displaced in contact regions with the joining materialmoldings (35).
 7. The method according to claim 2, characterized in thatthe joining material moldings (35) are applied to the base contact bumps(31) covered by matrix material (32), a local liquefaction of the matrixmaterial takes place in the region of the base contact bumps as a resultof laser action and during application of the joining material moldings(35) to the base contact bumps (31), the matrix material (32) isdisplaced in the contact regions with the joining material moldings(35).
 8. The method according to claim 6, characterized in that afterdisplacement of the matrix material (32) in contact regions with thejoining material moldings (35) the matrix material is transferred to thesolid state.
 9. The method according to claim 8, characterized in thatthe matrix material (32) is transferred to the solid state bypolymerization.
 10. The method according to claim 9, characterized inthat the polymerization takes place as a result of local action of laserenergy on the matrix material (32) in the peripheral region of thecontact bump tops (37).
 11. The method according to claim 9,characterized in that a material provided with additives for thereduction of oxides, at least on its surface, is used as matrix material(32).